Thickness-dependent flexoelectric response induced by torsional shear in BT-PVDF composite films

The flexoelectric effect has gained significant attention due to its potential applications in flexible sensing, energy harvesting, and structural health monitoring. While bending deformation is typically considered the primary trigger for flexoelectricity, torsional deformation can also induce notable flexoelectric responses through shear strain gradients. This study investigates the flexoelectric behavior of BT-PVDF composite films under torsional deformation, with a particular focus on the influence of film thickness on the response magnitude. The results show that film thickness significantly affects the distribution of strain gradients and charge separation efficiency, thereby modulating the flexoelectric response strength. By integrating experimental data with theoretical modeling, the underlying physical mechanisms governing this thickness-dependent flexoelectric behavior are revealed. Additionally, the capability of the composite film to detect torsional deformations in coaxially connected rod structures is validated. Experimental findings demonstrate that the film can precisely identify minor torsional damage, offering a high-sensitivity solution for structural health monitoring. This study highlights the potential of shear-torsion flexoelectricity for advanced sensing applications and lays the foundation for future developments in flexoelectric-based technologies.